1. Field of the Invention
The present invention relates to dryers. More particularly, the present invention relates to dryers that automatically sense clogged filters and that notify users when filter service is required.
2. Background of the Related Art
There are two basic types of dryers. Exhaust dryers dry using external air, while dehumidification dryers dry by dehumidifying internally circulated air.
FIG. 1 illustrates a typical exhaust dryer. As shown, the dryer includes a drum 20 inside a case 10. A driving unit 30 rotates the drum 20 so as to turn any laundry or other wet items within the drum. A heater 25 is located in a suction casing 22 behind the drum 20. A fan 35 inside an exhaust casing 27 in front of and below the drum 20 draws air into the suction casing 22, past the heater 25 (which heats the air), through the drum 20, and through the exhaust casing 27.
Still referring to FIG. 1, the dryer has a front opening 11. A door 15 can be opened to enable entry and removal of items into and out of the drum. When closed, the door 15 renders the drum 20 airtight. The driving unit 30 includes a double-shaft motor 31 that simultaneously turns the fan 35 and the drum 20. A pulley 32 on the motor 31, together with a belt 33 around the pulley 32 and the drum 20, transfer rotational forces to the drum 20.
As noted, a suction port 20a behind the drum 20 passes heated air into the drum 20. An exhaust port 27a in the exhaust casing 27 passes exhausted air from the drum 20 along and out an exhaust path 27b. As shown, a filter 40 is located in the exhaust path 27b. That filter collects (traps) particles, such as lint, that are produced during drying.
While generally successful, eventually the collected (trapped) particles build up such that the filter 40 becomes clogged. This significantly reduces airflow, and consequently drying efficiency. Therefore, periodically the filter 40 should be exchanged, cleaned, or otherwise serviced. Otherwise, drying efficiency will continue to drop, causing increased power consumption, longer drying times, and a dissatisfied user.
Unfortunately, the state of the filter (whether it is or is not clogged) is not obvious to a user. One reason for this is that the dryer provides no indication that filter service is required. Therefore, a clogged filter sensor would be beneficial. Even more beneficial would be a dryer that senses a clogged filter and that notifies a user that filter service, such as replacement or cleaning, is required.
Accordingly, the present invention is directed to a dryer having a filter sensing system that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An advantage of the present invention is a dryer having a filter sensing system that informs a user of a clogged filter. Beneficially, the filter sensing system senses a clogged filter when a predetermined temperature difference occurs between the air entering the filter and the air exiting the filter. Also beneficially, the filter sensing system notifies a user to service (possibly replace) the filter in time to avoid problems caused by a clogged filter.
Additional advantages, objects, and features of the invention will be set forth in the description which follows and/or will become apparent to those having ordinary skill in the art upon examination of the following, and/or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and the claims, as well as the appended drawings.
To achieve these advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a filter sensing system according to the present invention includes a filter inside a dryer exhaust casing for collecting particles in exhaust air. An inlet temperature sensor senses the temperature of the air that enters the filter, and an outlet temperature sensor senses the temperature of the air that exits the filter. A control unit uses the sensed temperature difference to determine when filter service is required.
Preferably, one of the temperature sensors is installed at an exhaust port between the drum and the filter inlet, while another temperature sensor is located behind the filter (in the air stream that leaves the filter).
Suitable temperature sensors include thermistors. Such thermistors are beneficially used as elements of a Wheatstone bridge circuit. In practice, the filter sensing system further includes a notice unit that informs a user when filter service is beneficial. Preferably, the control unit produces an alarm signal that actuates the notice unit when the temperature difference sensed by the temperature sensors exceeds a predetermined value. Suitable notice units include audio alarms and visual signals.
In another aspect of the present invention, a dryer includes an exhaust casing that receives air from a drum. A filter in the exhaust casing filters particles in the air from the drum. Temperature sensors are located in front of and behind the filter. The temperature sensors sense the temperature of the air that enters the filter and the temperature of the air that leaves the filter. A control unit receives temperature information from the temperature sensors. Based on that information, the control unit determines a state of the filter and causes a notice unit to signal that state.
Beneficially, the temperature sensors are thermistors. Preferably, the thermistors are electrically configured as elements of a Wheatstone bridge circuit. Preferably, the control unit actuates the notice unit when the temperature difference between the air that enters the filter and the air the leaves the filter exceeds a predetermined value. Suitable notice units include audio alarms and/or visual signals.
In a further aspect of the present invention, a dryer having a filter sensing system includes a rotating drum in a case, an exhaust casing that receives air from the drum, and a filter in the exhaust casing through which the received air passes. Additionally, temperature sensors in front of and behind the filter sense air temperature. Based on the output of the temperature sensors, a control unit determines a state of the filter, and produces an alarm signal that causes a notice unit to inform the user about the determined state of the filter.
Preferably, the temperature sensors are thermistors. In one embodiment, the control unit causes the notice unit to signal the state of the filter when the temperature difference sensed by the thermistors exceeds a predetermined value.
More preferably, at least one of the temperature sensors is installed in an exhaust port between the drum and the exhaust casing and in front of the filter. Additionally, at least one of the temperature sensors is inside the exhaust casing behind the filter.
Beneficially, the dryer includes a display unit that displays information regarding drying controls. In that case, the notice unit can include a portion of the display unit.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.